Wow! For such a brief question, you’re in for a lot of information. First, there are a lot of questions that someone could ask where the right verb is obvious. Question: Were you at the theatre last night? Answer: I was. Or you could say, “We were,” if there were a bunch of you seeing the show.
I suspect what you’re really confused about is what we call subjunctive mood and the clue is the word ‘wish.’ When you wish for something that isn’t or is contrary to what really is, then you use ‘were.’ So, you would say, “I wish I were young again,” because you can never be young again. Or you would say “If I were you, I wouldn’t do that,” because you can never be the person in question.